The Osteology and Relationships of the Echelid Eel, 
Kaupichthys diodontus 1 
William A. Gosline 2 
INTRODUCTION 
The main functions of the present paper 
are to demonstrate that two very different 
families of eels have hitherto been included 
under the "Echelidae” and to allocate these 
families to their proper positions in the order 
Anguilliformes (or Apodes). In order to 
establish these points, the osteology of Kau- 
pichthys diodontus Schultz is dealt with in 
some detail. 
On September 7, 1949, an unripe female 
of this species, 155 mm. long, was taken by 
Strasburg, Welsh, and the author in a poison 
station in shallow water off the aquarium at 
Waikiki, Oahu, Territory of Hawaii. The 
species (and genus) was originally described 
by Schultz (1943: 50, pi. 6 and text fig. 5 i) 
from Tau and Rose Islands in the Samoan 
group. It is hitherto unrecorded from Ha- 
waii. The specimen at hand differs from 
Schultz’s description (and from a Bikini 
specimen dealt with below) as follows: the 
teeth are blunter than indicated in his diag- 
nosis and figure (5 /) ; the two rows of vome- 
rine teeth are not so widely separated, nor 
do they extend farther posteriorly than the 
maxillary rows; and finally, the maxillary 
teeth are quite distinctly set apart from the 
premaxillary and vomerine groups. Whether 
the Hawaiian form merits specific or subspe- 
cific distinction, or whether the above-men- 
tioned differences are merely individual or 
size variations, I do not have sufficient mate- 
rial to decide. 
Contribution No. 3, Hawaii Marine Laboratory. 
2 Department of Zoology, University of Hawaii. 
Manuscript received February 27, 1950. 
In identifying the Waikiki specimen I be- 
came doubtful as to its relationship with the 
other Hawaiian genus — Muraenichthys — 
which has always been placed in the same 
family with it (Schultz, 1943: 49; Schultz 
and Woods, 1949: 170). A specimen of 
Kaupichthys diodontus from Bikini, one of 
the duplicates very kindly sent me by Dr. 
Schultz, permitted an osteological investiga- 
tion of that species. From this examination 
it is very apparent that Kaupichthys and 
Muraenichthys do not belong in the same 
family; in fact they belong on opposite sid§s 
of the major division of the eels as classified 
by Regan (1912) and Trewavas (1932). 
An account of the osteology of Kaupichthys , 
based on the 100 mm. specimen from Bikini, 
follows. The specimen was stained in aliza- 
rin and the head dissected; the remainder 
of the specimen was cleared in potassium 
hydroxide. 
OSTEOLOGY 
The lateral line canals of the body and 
head are enclosed in a series of small bony 
ossicles except where they penetrate the skull 
bones. That of the body gives rise to only 
two pores leading to the exterior; these are 
both forward of the pectoral (Fig. 1). In 
the head region the sensory canal system is 
of rather normal eel pattern (Trewavas, 
1932, pi. Ah and text fig. 3A), though the 
number of pores leading to the surface of 
the head is somewhat reduced. A longitu- 
dinal canal (11) connects the lateral line of 
the body with that of the head system. As 
is usual in eels, a transverse canal (tc) run- 
[ 309 ] 
